Metal Site Substitution and Role of the Dimer on Symmetry Breaking in FePS₃ and CrPS₄ under Pressure

Abstract

We combine infrared absorption, Raman scattering, and diamond anvil cell techniques to explore the properties of FePS3 and CrPS4 under pressure, comparing our findings with a symmetry analysis, lattice dynamics calculations, and an examination of the energy landscape. Although these complex chalcogenides are considered to be members of the same family of materials, they display remarkably different phase progressions on account of the metal center orbital filling, character of the P–P linkage, layer corrugation, and differing size of the van der Waals gap. We discuss the space group progressions, structure–property relations, and development of pressure-induced metallicity in terms of the competition between local and long-range symmetry transformations and structural distortion pathways. These findings place the properties of FePS3 and CrPS4 on a firm foundation for work under strain control and in the single layer limit.

Insulator–metal transition in CrSiTe3 triggered by structural distortion under pressure

“…The space group in the narrow high-pressure region between the structural phase transition and the insulator-metal transition is also of interest. Unfortunately, the phonons are heavily screened in this bad metal region, making it difficult to analyze symmetry breaking and carry out a subgroup analysis 20,22 . We can, however, state that the high-pressure vibrational properties of CrSiTe 3 above the two-phase region are inconsistent with the R3 space group that has been proposed for CrGeTe 3 7 because the infrared spectra of CrSiTe 3 provide no evidence for a loss of the inversion center which is expected for a transition to a polar space group.…”

Li-ion intercalation-driven control of two-dimensional magnetism in van der Waals FePS3 bilayers

“…20,45 The vdW gaps between two adjacent FePS 3 monolayers, defined as the shortest distance between the S sublayers (see Fig. S2 in the ESI†), are approximately 3.38 Å 20 and 3.26 Å 46 for 3D bulk FePS 3 . These gaps result in an indirect exchange path along the c -axis, giving the FePS 3 crystal highly anisotropic behaviors.…”

Novel Light-Matter Interactions in 2D Magnets

“…The P atom is coordinated in the center of three CrS 6 octahedra. The weak vdW force is between sulfur layers, as shown in Figure 4a [49][50][51].…”